The present invention relates to plywood lay-up technology, and more specifically, to conveyor-type lay-up systems capable of laying-up a range of plywood products.
Conventionally, plywood lay-up may be accomplished by a conveyor lay-up line or at a stationary assembly station. Plies of face and center long grain veneer are laid with intervening plies of cross grain fragments or one-piece core, and glue is applied at some stage of the process between plies. The glue is cured under heat and pressure, to produce standard plywood sheets having substantially equalized strength in both grain directions.
On a conveyor type lay-up line, each step is conventionally carried out in line sequence along the lay-up line, and one ply at a time is placed on the conveyor. For example, for a typical 5-ply sheet, a long grain back ply, a crossband core, a long grain center ply, a second crossband core, and a long grain face ply are stacked in order. The crossband cores may be arranged random core, or one-piece spliced core. Adhesive may be applied by spray or curtain coat to one side of long grain plies or cores as they are laid, or may alternatively be applied by roller to both sides of a core ply as it is laid. Typically, each ply is provided to a conveyor by an auxiliary feeder, able to supply the main lay-up line at a rate matching the lay-up line feed rate. Each ply in the stacking order requires a dedicated feeder, and each dedicated feeder is placed along the lay-up line in the order that the ply is stacked in the final laminated sheet.
Given that each conventional face or center feeding machine and each crossband core feeding machine occupies a space adjacent to the conveyor in a certain order, and that each machine has only alternatives of laying a ply or doing nothing, then a conventional conveyor-type line has very little flexibility in product range. The lack of flexibility in products is a serious shortcoming of the conventional conveyor-type lay-up line.
Conventionally, to augment the range of possible products to be made by a typical lay-up line, specific assemblies of plywood lay-up must be determined, then the required individual machines added for each assembly. Each machine serves a single function, and the line becomes extremely long. Thus, using conventional lay-up techniques, a flexible lay-up line becomes very long, and is therefore extremely difficult to establish in an existing facility.
However, the linear movement of stacked plies along a lay-up line is a conventional and well understood process. To radically change the processing technique introduces new control, transportation, post-processing, and training issues. It is difficult to integrate a device having improved flexibility to the line.